Spectral and thermal study on the adduct formation between square planar nickel(II) chelates and some bidentate ligands

Adducts of Ni(II)-square planar complexes [Ni(β-dik)(Me4en)]+, with a series of bidentate ligands (L), where β-dik = acetylacetonate (acac) and benzoylacetonate (bzac), Me4en = N,N,N′,N′-tetramethylethylenediamine and L = Me4en, 2,2′-bipyridine (bipy), ethylenediamine (en) and oxalate (C2O42−) have been synthesized and characterized by spectral, thermal and magnetic measurements. Formation constants of the adducts formed from a series of ternary mixed Ni(II) complexes with the general formula [Ni(β-dik)(diam)]+ with 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy) and pyridine were spectrophotometrically determined. Thermodynamic parameters of the adduct formation between nickel(II) square-planar chelates and pyridine (py), 2,2′-bipyridine (bipy) and acetylacetone (acac) were also spectrophotometrically determined in 1,2-dichloroethane. The thermal stability of the isolated adducts was studied using thermogravimetry and the decomposition schemes of the adducts were given.